Automatic draft controller

Abstract

A draft control plate, which automatically opens or closes to provide efficient draft conditions in a furnace, is provided with both horizontal and vertical counterbalance devices which respectively permit adjustment of the initial position of the plate and the sensitivity of its movements. Initially, the plate is partially open where it remains while the furnace is operating under normal conditions. It is then capable of opening or closing in response to changes in the pressure differential across it. Preferably, the plate is horizontally mounted in an auxiliary flue channel which is adjacent to and in connection with the main flue of the furnace.

What is claimed is: 
     
       1. A method for draft control in a furnace having air regulators on its burners and a draft control plate mounted so as to be in communication with its flue, comprising the steps of: (a) initially setting said plate in a closed position to permit the purging of said furnace;   (b) adjusting the air regulator to be approximately half open;   (c) initially setting said plate partially open to permit it to automatically open or close in response to changes in draft velocity due to changes in ambient and/or operating conditions;   (d) starting the furnace and monitoring the efficiency of its combustion;   (e) adjusting the position of said plate so that efficient operating conditions are achieved in said furnace while at the same time said air regulators are approximately half open; and   (f) adjusting the air regulators to maintain said efficient operating conditions.   
     
     
       2. The method of claim 1 further including the step, prior to step (a) of adjusting the sensitivity of said plate's movements in response to changes in pressure differential. 
     
     
       3. A method for controlling the draft in a furnace having air regulators to regulate the amount of air entering the burners of said furnace, a draft plate adapted to be in communication with both the outside air and with the flue of said furnace, a counter-weight means attached to said plate for initially setting said plate in an open position, and adjustment means for varying the sensitivity of the movements of said plate, comprising the steps of: (a) adjusting said adjustment means to provide for the appropriate degree of sensitivity of said plates movements in response to changes in operating conditions, said adjusting step primarily taking into consideration changes in ambient conditions;   (b) adjustng said burner air regulators to be approximately one-half open;   (c) adjusting said counter-weight means to set said plate in an open position;   (d) starting said furnace and monitoring the efficiency of its combustion; and   (e) adjusting said counter-weight means and said air regulators so that efficient operating conditions are automaticaly achieved and maintained in said furnace by the response of said plate to changes in ambient conditions while at the same time said air regulators are approximately one-half open.   
     
     
       4. A method for controlling the draft in a furnace having an auxiliary channel adapted to be in communication with the outside air and with the flue of said furnace, an auxiliary damper mounted in said channel for selectively restricting the passage of outside air in said channel, and a draft control plate also mounted in said channel, comprising the steps of: (a) initially closing said draft plate to permit the purging of air and gases from said furnace;   (b) setting said plate in a partially open position;   (c) starting said furnace and permitting it to reach normal operating temperature;   (d) modifying the partially open position of said plate in order to automatically achieve efficient combustion in said furnace due to the response of said plate to changes in operating conditions; and   (e) adjusting the position of said auxiliary damper in order to enhance the sensitivity of said automatic draft control plate and to promote efficient operating conditions in said furnace.